<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <ul>
        <li>1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
        <li>6</li>
        <li>7</li>
        <li>8</li>
        <li>9</li>
        <li>10</li>
    </ul>

    <a href="http://www.baidu.com">百度</a>
    <form action="http://www.baidu.com">
        <input type="submit">
    </form>
    <script>
        var ul = document.querySelector('ul')
        var li = document.getElementsByTagName('li')
        var a = document.querySelector('a')
        var form = document.querySelector('form')
        
        ul.addEventListener('click', function () {
            console.log(100)
        })

        a.addEventListener('click', function (e) {
            e.preventDefault()
            console.log('a')
        })
        form.addEventListener('submit', function (e) {
            e.preventDefault()
            console.log('form')
        })
    </script>
</body>

</html>